Deep stall aircraft landing

ABSTRACT

An aircraft defining an upright orientation and an inverted orientation, a ground station; and a control system for remotely controlling the flight of the aircraft. The ground station has an auto-land function that causes the aircraft to invert, stall, and controllably land in the inverted orientation to protect a payload and a rudder extending down from the aircraft. In the upright orientation, the ground station depicts the view from a first aircraft camera. When switching to the inverted orientation: (1) the ground station depicts the view from a second aircraft camera, (2) the aircraft switches the colors of red and green wing lights, extends the ailerons to act as inverted flaps, and (3) the control system adapts a ground station controller for the inverted orientation. The aircraft landing gear is an expanded polypropylene pad located above the wing when the aircraft is in the upright orientation.

The present application is a Continuation Application of U.S.application Ser. No. 16/271,916, filed Feb. 11, 2019, which is aContinuation Application of U.S. application Ser. No. 15/611,723, filedJun. 1, 2017, now U.S. Pat. No. 10,204,522, which is a ContinuationApplication of U.S. application Ser. No. 14/936,632, filed Nov. 9, 2015,now U.S. Pat. No. 9,672,748, which is a Continuation Application of U.S.application Ser. No. 13/261,814, having a 371(c) date of Jul. 29, 2014,now U.S. Pat. No. 9,208,689, which is a National Stage application ofInternational Application Serial No. PCT/US2012/000358, filed Aug. 16,2012, which claims the benefit of U.S. Provisional Application No.61/575,417, filed Aug. 19, 2011, each of which is incorporated herein byreference for all purposes.

The present invention relates to an aircraft configured to fly in anupright orientation and land in an inverted orientation.

BACKGROUND OF THE INVENTION

Unmanned aerial vehicles (UAVs) have been developed for a large array oftasks. One such UAV task is for aerial reconnaissance. In UAVreconnaissance aircraft, a payload consisting of one or more cameras,and possibly one or more gimbaled supports for the cameras, mightpreferably extend below the fuselage and/or wing of the aircraft formaximum unimpeded viewing during flight. This configuration potentiallyputs the cameras and gimbals in harm's way during landing, particularlyfor payloads that are sensitive to high vibration and impact loads.

Larger UAVs tend to have a significant range (distance they can travel),and are typically provided with standard aircraft take-off and landingfacilities. These aircraft do not typically have to take off and land incombat settings in which the visual exposure of the ground crew may belife threatening. Moreover, larger UAVs are naturally required to havelanding gear configurations that are structurally size appropriate totheir aircraft, which may be significantly larger than the payload sizerequirements for a reconnaissance payload. Thus, the landing gearconfiguration for larger UAVs tends to be such that the payload isstructurally supported and protected during landing. Moreover, the costof such an aircraft is generally large in comparison to the cost of itspayload, so the payload may be made structurally tolerant withoutsignificantly increasing the overall cost of the combined aircraft andpayload.

Smaller UAVs are often used in military field situations, in whichlittle or no room is available for rolling landings, and in whichprecision landings are important to limit the exposure of fieldpersonnel to enemy fire. Precision landings are also useful whenattempting to land the aircraft in a limited location such as a rooftop.Likewise, in civilian applications, similar needs may be found in urbansettings for which only a limited ground space is controlled during anemergency situation, such as near a burning building. For smaller UAVs,a number of adaptations have been used to protect low-hanging payloadintegrity during landing. One adaptation is to use payloads having highstructural integrity (such as using only sturdy, non-gimbaled cameras)to provide for payloads that are tolerant to the high vibration andimpact loads that occur when the payload strikes the ground.

For example, the Raven® UAV, with a wingspan over 4 feet, provideslow-altitude surveillance and reconnaissance intelligence for bothmilitary and commercial applications. Such an aircraft can be configuredwith a cushioned landing pad (in place of landing gear) that allowsprovide for an extremely short-field landing (at the expense of muchhigher landing loads). The relatively accurate short field landingcapability does help protect ground crews from the possible dangers ofopen exposure (e.g., in military situations).

This aircraft may also be equipped with a payload of a group of robuststationary cameras that can handle the high landing loads. Nevertheless,high resolution cameras of such structural integrity can be veryexpensive. Given that smaller UAVs are significantly less expensive thatlarge UAVs, providing a group of highly expensive cameras to a small UAVcan add significantly to the cost of the aircraft. Alternatively, suchan aircraft can be configured with the entire payload being gimbaled notonly for a wide field of viewing, but also such that it swings up intothe fuselage prior to landing. While this may be effective to reduce thelanding loads on the payload, the gimbal mechanism adds significantweight, and the need to fit it within the fuselage limits the size andshape of the payload.

Another known adaptation for smaller UAVs is to use a parachute to landthe aircraft. In such a maneuver, the engine is stopped and theparachute is deployed while the aircraft is in the general vicinity ofthe desired landing location. Moreover, the parachute can be attached tothe bottom of the aircraft to provide for the aircraft to land not onits lower surface, but rather on its upper surface (which can includelanding struts to support the vehicle during a vertical-decent landing).If the timing of such a deployment is accurate, the winds arecooperative, and the parachute both successfully deploys andsuccessfully inverts the aircraft without tangling in part of theaircraft structure, then a landing within a limited field location withlimited landing loads might be possible.

Nevertheless, this involves surrendering flight control once a parachuteis deployed, and thus greatly reduces the likelihood of a preciselanding location. Also, a parachute landing is also difficult to“call-off” if landing the aircraft is no longer desired, the landingtrajectory is incorrect, or the landing site is no longer cleared. Suchissues could be extremely important in a situation where landinglocation is important, such as needing to land an aircraft on a rooftopor near a protected enclosure for ground personnel. Moreover, the skilllevel required to properly estimate a landing location in situations ofvarying wind speed and direction conditions might be higher than theskill level otherwise required for use of the aircraft.

Accordingly, there has existed a need for an unmanned vehicle capable ofaccurate landings with a load sensitive payload that extendssignificantly from the bottom of the aircraft. Preferred embodiments ofthe present invention satisfy these and/or other needs, and providefurther related advantages.

SUMMARY OF THE INVENTION

In various embodiments, the present invention solves some or all of theneeds mentioned above, providing a related method (and a relatedapparatus) for rapidly landing an aircraft in a tightly controllablemanner and landing location. The aircraft has a wing including an uppersurface, a lower surface, and defining and an upright orientation fornormal aircraft flight and an inverted orientation for inverted flight.The upper surface is gravitationally above the lower surface while inthe upright orientation, and the lower surface being gravitationallyabove the upper surface while in the inverted orientation.

Under the steps of the invention, the operation of one or more controlsurfaces is controlled to approach the landing location while theaircraft is flying in the upright orientation. The operation of the oneor more control surfaces is then controlled to invert the aircraft suchthat it is controllably moving in an inverted orientation. The operationof the one or more control surfaces is then controlled to at leastpartially stall the wing while in the inverted orientation to providefor the aircraft to rapidly descend.

Advantageously, under this method the aircraft can rapidly andcontrollably descend from standard flight to the landing location.Payloads that descend below the wing are protected from contacting theground due to the inverted orientation. Prior to landing an operator canchoose to abort the landing by using the control surfaces to reorientthe plane to an upright flight orientation. The rate of descent can becontrolled by controlling depth of the wing stall.

Other features and advantages of the invention will become apparent fromthe following detailed description of the preferred embodiments, takenwith the accompanying drawings, which illustrate, by way of example, theprinciples of the invention. The detailed description of particularpreferred embodiments, as set out below to enable one to build and usean embodiment of the invention, are not intended to limit the enumeratedclaims, but rather, they are intended to serve as particular examples ofthe claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an aircraft embodying the presentinvention.

FIG. 2 is a right side view of the aircraft depicted in FIG. 1, in anupright orientation.

FIG. 3 is a right side view of the aircraft depicted in FIG. 1.

FIG. 4 is a bottom view of the aircraft depicted in FIG. 1.

FIG. 5 is a bottom perspective view of a wing center section and thrustmodule of the aircraft depicted in FIG. 1, having a battery and acontrol module cover removed.

FIG. 6 is an enlarged view of FIG. 2.

FIG. 7 is a perspective view of a remote-control station that is part ofan aircraft system including the aircraft depicted in FIG. 1.

FIG. 8 is a schematic view of an aircraft system control system for theaircraft system including the aircraft depicted in FIG. 1 and the remotecontrol station depicted in FIG. 7.

FIG. 9 is a time varying depiction of a first variation of a landingmaneuver for the aircraft system.

FIG. 10 is a time varying depiction of a second variation of a landingmaneuver for the aircraft system.

FIG. 11 is a schematic view of functions carried out by the aircraftsystem control system depicted in FIG. 8.

FIG. 12 is a schematic view of a method embodying the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention summarized above and defined by the enumerated claims maybe better understood by referring to the following detailed description,which should be read with the accompanying drawings. This detaileddescription of particular preferred embodiments of the invention, setout below to enable one to build and use particular implementations ofthe invention, is not intended to limit the enumerated claims, butrather, it is intended to provide particular examples of them.Furthermore, there is no intent to be bound by any expressed or impliedtheory presented in this application.

Typical embodiments of the present invention reside in an unmannedaerial vehicle (“UAV”) (i.e., an unmanned aircraft system) including aUAV configured to invert prior to landing, and then go in to acontrollable stalled flight condition that provides for rapid butcontrolled descent.

UAV Aircraft

With reference to FIGS. 1 to 4, a first embodiment of an aircraft underthe invention is configured with a wing 101 connected to an empennage103 by a fuselage including a tail-boom comprised primarily of a slendershaft 107 extending between the wing and empennage. The wing has anupper surface 111 and a lower surface 113 that define the camber of thewing and an upright (flying) orientation of the aircraft for normalaircraft flight. With the wing in the upright orientation, the uppersurface faces gravitationally upward and is gravitationally above thelower surface, and the lower surface faces gravitationally downward. Theupper and lower wing surfaces further define an inverted (flying)orientation for inverted aircraft flight, in which the lower surfacefaces gravitationally upward and is gravitationally above the uppersurface, and the upper surface faces gravitationally downward.

The camber is chosen to be an airfoil that can operate relativelyefficiently (as compared to other airfoils) in the upright orientation,and that is not highly unstable in the inverted orientation. Theselection of such an airfoil can be made by a person skilled in the artusing experimentation or analytical methods.

The empennage 103 has an elevator 115 (i.e., a horizontal controlsurface) and a rudder 117 (i.e., a vertical control surface), thedeflection of which are controlled by servos on a slender, base section119 of the empennage. Rather than extending upward, the rudder extendsdownward from and below the base section, elevator and fuselage when theaircraft is in the upright orientation. It should be noted that withthis embodiment in the upright orientation, the rudder would likelystrike the ground if the aircraft were to land.

While the elevator 115, rudder 117 and base section 119 substantiallycomprise the complete empennage in this embodiment, an embodiment alsohaving rigid horizontal and vertical stabilizers are within the scope ofthe invention. In the case of the vertical stabilizer, it will likelyextend downward from and below the base section, elevator and fuselage,just as the rudder does.

The wing 101 includes a center section 121 and two laterally extendingtip sections including a port tip section 123 and a starboard tipsection 124. It should be noted that in this application, the termsstarboard and port refer to the right and left hand sides of the wing(and more broadly, of the aircraft), respectively, when the plane is inthe upright orientation, as it is commonly understood for aircraft. Forthe purposes of this application, it should be understood that invertingthe aircraft does not alter which physical portion of the wing is on theport side and which physical portion of the wing is on the starboardside.

With reference to FIGS. 1-5, mounted on the center section 121 are athrust module 125, two ailerons 127 configured to be actuated by servos128 at inboard ends of the ailerons, and a control module 129. Thecontrol module forms a single, watertight compartment covered by acontrol module cover, and that holds most of the electronics necessaryfor flying the aircraft. While this embodiment includes common types ofcontrol surfaces (e.g., ailerons 127, an elevator 115 and a rudder 117),it should be understood that the use of other, less common types ofcontrol surfaces (e.g., canards and ruddervators) are within the scopeof the invention.

Extending forward from a leading edge 131 of the wing 101, the thrustmodule 125 forms a support structure holding a motor 133 configured todrive a propeller 135 in rotation to provide thrust for the aircraft.The thrust module also forms a battery cavity 137 configured to hold abattery 139 for powering the aircraft. Power is controllably provided tothe motor by the battery, and motor operation is controlled viaelectrical leads extending from the control module 129.

Included within the control module 129 are GPS antennas 141, a GPSreceiver 143, a user interface 145, a video processing unit 147, aminiature digital data link 149 (“DDL,” i.e., a lightweight andlow-power broadband digital network node that enables enhanced commandand control of small unmanned aircraft systems), an inertial measurementunit 151 (“IMU”), and various communication equipment configured fortransmitting and receiving communication signals. Also included withinthe control module are two beacon boards, including a port beacon board153 on the port side of the wing, and a starboard beacon board 155 onthe starboard side of the wing.

The beacon boards are provided with navigation lights including astarboard light 157 connected to the starboard beacon board 155 on thestarboard side of the wing, and a port light 159 connected to the portbeacon board 153 on the on the port side of the wing. These navigationlights are configured to be visible both on the upper and lower surfacesof the wing. This may be accomplished using a single light locatedbetween transparent surfaces on the upper and lower surfaces of thewing, or using separate, upper and lower lights for each side of thewing. Each of the navigation lights are configured to controllably emitat least two different colors of light, which will typically be greenand red.

The center section is further provided with other devices useful for theoperation of civilian and/or military unmanned aircraft, such as a pitottube 161, a dipole antenna 163, an analog uplink or connection for aselective availability anti-spoofing module (“SAASM”) key 165, whichprovides for secure reception of the U.S. military's precise positioningservice. The pitot tube is preferably configured for operation in a widevariety of whether conditions, including rain.

With reference to FIGS. 1-6, extending down from the wing 101 is apayload including a first camera system 171. This camera system isconfigured with a high resolution infrared/electro optical camera 173supported on a gimbal 175 that is driven by one or more motors in acamera servo system 177. This payload extends gravitationally below thewing (and fuselage) while the aircraft is in the upright orientation,and typically, below all other parts of the aircraft, except perhaps therudder 117. Like the rudder, in the upright orientation the payloadmight strike the ground if the aircraft were to land. The camera systemis controllable to look in different directions using the gimbal.Nevertheless, it is configured such that it can view downward andforward while the aircraft is in the upright orientation. Thus, thefirst camera system making operate as a first, upright-orientationflight camera. This first camera is configured to support visual flightcontrol of the aircraft while it is flying in the upright orientation.

Alternatively, (or in addition to a payload camera) the aircraft couldhave a fixed, first, upright-orientation camera oriented to lookdownward and forward while the aircraft is in the upright orientation.In either case, this first camera is configured to support visual flightcontrol of the aircraft while it is flying in the upright orientation.Such a fixed, first, upright-orientation flight camera allows for theuse of payloads that do not have a camera configured to support visualflight control of the aircraft, or for the gimbaled camera to be used indirections that would not support flight control by a user.

Embedded in the fuselage or wing 101 is a second camera system 181including a second, inverted-orientation camera 183 oriented to lookdownward and forward while the aircraft is flying in the invertedorientation. This second camera system is configured to support visualflight control of the aircraft while it is flying in the invertedorientation, and more particularly, to support controlled descent whilelanding in the inverted orientation.

The aircraft includes landing gear 191. Rather than being located forlanding in an upright orientation (as is known), the landing gear islocated and positioned with respect to the fuselage and wing 101 suchthat the landing gear is useful for landing the aircraft while theaircraft is in the inverted orientation.

For the purposes of this application the term landing gear should bebroadly construed to cover structures configured to impact the groundduring landing. For this embodiment, the landing gear 191 is an expandedpolypropylene pad located gravitationally above the wing 101 and payload(i.e., the first camera system 171) when the aircraft is flying in theupright orientation. The pad provides a significant level of cushioningupon impact, and provides for the aircraft to come to rest quickly uponlanding. It should be understood that other, more standard types oflanding gear (such as wheels or landing struts) that are located andpositioned for landing the aircraft while inverted are within the scopeof the invention.

It is noteworthy that the payload, and particularly the first camerasystem 171 extends gravitationally below the wing 101 and landing gear171 while the aircraft is in the upright orientation, providing thepayload with clear line-of-sight viewing and/or targeting in manydirections. The landing gear being located and positioned for landingthe aircraft while inverted allows for the payload to be out of harm'sway during the landing, and provides for the landing gear and aircraftstructure to cushion the shock of landing for the payload. Thus, thepayload, which might be a very expensive component of the aircraftsystem, is well protected.

Remote-Control Station

With reference to FIG. 7, the aircraft system further includes aremote-control station 201, which will typically, but not necessarily,be used by a user/pilot on the ground (e.g., a ground station). Otherpossible user/pilot locations include a boat or a plane.

The remote-control station 201 is configured for the user/pilot toremotely control the aircraft. More particularly, the remote-controlstation includes a video monitor 203 for displaying both flight controlinformation (as is known for aircraft) and a live video feed from theaircraft to provide for visual flight, particularly for when theaircraft is not in view of the user. The remote control station furtherhas a manual controller 205 to control the various aircraft features andfunctions. Optionally, this controller may be of a type similar to thoseknown for video gaming such that the operation of the aircraft might bemore quickly learned by user/pilots familiar with video game controls.

To provide communication with the aircraft, the remote-control stationis provided with communication equipment 207 configured for thetransmission and receipt of communication signals 209. As was previouslydescribed, The aircraft is also provided with communication equipmentconfigured for the transmission and receipt of the communicationsignals, and thus the remote-control station is provided with two-waycommunication with the aircraft. These communication signals may includeflight control information and commands, and payload related signals.

System Control System

With reference to FIGS. 7 & 8, the aircraft system, including both theaircraft and the remote-control station 201, is provided with a systemcontrol system 301 configured for a user to remotely control the flightof the aircraft using the remote-control station. The system controlsystem includes an aircraft control system 303 that includes thehardware and software within the aircraft, and a station control system305 that includes the hardware and software within the remote-controlstation. The aircraft control system and station control systemcommunicate with each other using the communication signals 209 that theaircraft and remote-control station are equipped to transmit andreceive.

The station control system 305 is provided with an auto-land button 211that activates an auto-land function. The auto-land button may beaccessible to the remote-control station user as a physical button (asdepicted), or an-onscreen button (such as one that can bepressed/activated using a mouse or a finger on a touchscreen). When theauto-land button is activated by the user, the auto-land functionprovides for the station control system to send an auto-landcommunication signal or set of signals that cause the aircraft controlsystem 303 to deflect the control surfaces of the aircraft such that theaircraft enters and performs an inverting maneuver in which the aircraftrotates from the upright orientation to the inverted orientation. Thisoccurs in an automated manner without further intervention by the user.

The inverting maneuver may be any of a plurality of known inversionmaneuvers. With reference to FIG. 9, for example, the inversion maneuvermay be a 180 degree roll 401 of the aircraft from the uprightorientation 403 to the inverted orientation 405. In this maneuver, theaircraft will continuously fly in relatively the same direction 407.With reference to FIG. 10, as another example, the inversion maneuvermay be a 180 degree pitching maneuver 411 of the aircraft (i.e., onehalf of an upward or downward loop) from the upright orientation 403 tothe inverted orientation 405. In this maneuver, the aircraft will startflying in a first direction 413 and end up flying in substantially theopposite direction 415. The pitching maneuver might be more complicatedto use for a user wanting to land the aircraft in a specific location(as they will have to overshoot that location), but it may haveapplications in which it is preferable. Optionally, the user will havethe option of which type of maneuver to use, either by selecting fromone of two auto-land buttons, or from having a default maneuver form andthe ability to override the default form before selecting the auto-landbutton.

With reference to FIGS. 1-11, during inverted flight (i.e., while flyingin the inverted orientation), the system control system changes theoperation of the aircraft system as compared to its operation duringnormal, upright flight (i.e., while flying in the upright orientation).These changes may be initiated just prior to or during the transitionfrom the upright orientation to the inverted orientation, orsubsequently to that transition. These changes provide for a simple andseamless transition between the two orientations from the standpoint ofthe user. Typically these changes will occur, either directly orindirectly in response to the auto-land button being actuated (i.e.,physically or electronically selected) 431 (and/or the auto-landfunction being otherwise activated, such as by reaching the end ofavailable power for flight).

A first of the aircraft system operational changes in response toinverted flight pertains to monitoring visual flight references. Duringupright flight the first, upright-orientation camera is oriented to viewdownward and forward, while the second, inverted-orientation camera ispointed upward and forward. The system control system 301 is configuredsuch that, while the aircraft is in the upright orientation, theaircraft control system is configured to relay real-time video imagesfrom the first, upright-orientation camera 173 to the remote-controlstation, and the station control system is configured to display on themonitor 203 the relay real-time video images from the first,upright-orientation camera to the user so that the user may use theimages for visual flight.

During inverted flight the second, inverted-orientation camera 183 isoriented to view downward and forward, while the first,upright-orientation camera is pointed upward and forward. The systemcontrol system is configured such that, while the aircraft is in theinverted orientation, the aircraft control system is configured to relayreal-time video images from the second, inverted-orientation camera tothe remote-control station, and the station control system is configuredto display 433 on the monitor 203 the relay real-time video images fromthe second, inverted-orientation camera to the user so that the user mayuse the images for visual flight.

It should be noted that the change from displaying the first cameraimage to the second camera image may be accomplished in a number ofways. For example, the aircraft control system 303 may change thetransmission of images to be from the upright-orientation camera 173 tothe inverted-orientation camera 183, either in response to receiving acommunication signal 209 indicating the auto-land button 211 has beenactivated (and/or the auto-land function was activated), or in responseto directly sensing that the aircraft was in the inverted orientation.Alternatively, the aircraft control system could continuously transmitimages from both the first and second cameras, while the station controlsystem could change the display of images to be from theupright-orientation camera to the inverted-orientation camera, either inresponse to the auto-land button having been activated (and/or theauto-land function having been activated), or in response to acommunication signal from the aircraft control system indicating thatthe aircraft was in the inverted orientation.

In another variation of this change, the station control system 301 maybe configured to display a plurality of video image feeds. For example,a first image display area on the monitor 203 might be a flight-controldisplay, while a second image display area on the display might be amission-related image feed. This could be used, for example, when usingan upright orientation camera that is different from the payload camera,or when it is desirable to use the second camera to look upward inupright flight (such as when flying under a bridge and wanting toinspect the underside of the bridge). In these cases, the inversion ofthe aircraft will cause the system control system to change the cameraimage feed that is displayed in the flight control display.

As previously noted, the starboard light 157 and port light 159 eachhave the capability to emit two different colors of light, preferablybeing green and red. A second of the aircraft system operational changesin response to inverted flight pertains to the navigation lights. Duringupright flight, under the direction of the aircraft control system 303,the starboard light emits the first color (e.g., green), while the portlight emits the second color, e.g., red. These colors are viewable fromboth above and below their respective sides of the wing. This colorscheme conforms to traditional flight (and nautical) standards.Nevertheless, during inverted flight, under the direction of theaircraft control system 301, the colors are switched 435 such that thestarboard light emits the second color (e.g., red), while the port lightemits the first color, e.g., green. As with the flight control images,it should be noted that the timing and initiation of the change incolors may be accomplished based upon the receipt of a communicationsignal indicating the auto-land button has been activated (and/or theauto-land function has been activated), or in response to directlysensing that the aircraft is in the inverted orientation.

As should be apparent, this change provides for observers (including theuser) to be able to correctly judge the direction of travel after theaircraft has reached the inverted orientation. As was previouslyindicated, the starboard and port lights might be implemented usingseparate lights on the upper and lower surfaces of the wing. In avariation of this aspect particular aspect of the invention, only thelights on the gravitational bottom of the wing are illuminated. Thus,under the control of the aircraft control system, only the lights on thelower surface of the wing are illuminated during upright flight, whileonly the lights on the upper surface of the wing are illuminated duringinverted flight. It should be noted that this is still within the scopeof a system in which a starboard light and a port light each have thecapability to emit two different colors of light, as both the starboardlight and port light each has two parts, one being on the lower surfaceand one being on the upper surface.

As previously noted, the aircraft includes a set of one or more controlsurfaces (e.g., ailerons 127, an elevator 155 and a rudder 117)configured to control the flight of the aircraft. A third of theaircraft system operational changes in response to inverted flightpertains to control surface actuation. During upright flight, inresponse to user input, the station control system transmitscommunication signals to the aircraft control system, which in turncontrols the one or more control surfaces in known protocols foraircraft flight control. For example, while the aircraft is in theupright orientation, when the user actuates the controller to get theaircraft to pitch up, the aircraft control system rotates the trailingedge of the elevator upward with respect to the upper surface of thewing in order to pitch the aircraft gravitationally upward. Likewise,while the aircraft is in the upright orientation, when the user actuatesthe controller to get the aircraft to yaw left, the aircraft controlsystem rotates the trailing edge of the rudder to the port side.

During inverted flight the system control system 301 (either in theaircraft control system 303 or the station control system 305) altersthe control of some of the control surfaces with respect to the userinputs to present to the user an unchanged flight control experience.More particularly, the system control system is configured to adapt theoperation of the control surfaces 437 with respect to manual inputs onthe controller 205 such that a user of the controller does not need toadapt use of the controller based on the orientation of the aircraft.For example, in response to a pitch upward manual input while theaircraft is in the inverted orientation, the aircraft control systemrotates the trailing edge of the elevator downward with respect to theupper surface of the wing (i.e., gravitationally upward) in order topitch the aircraft gravitationally upward. Likewise, in response to ayaw left input while the aircraft is in the inverted orientation, theaircraft control system rotates the trailing edge of the rudder to thestarboard side in order to yaw the aircraft to the left with respect toits flight direction. Both of these motions are reversed over theupright-orientation variations.

As was previously described, the timing of this change in controlsurface movement may be accomplished based upon the generation orreceipt of a communication signal 209 indicating the auto-land buttonhas been activated (and/or the auto-land function has been activated),or in response to a direct sensing that the aircraft is in the invertedorientation. As should be apparent, this change provides for the user tofly the aircraft to a landing without having to reverse the operation ofsome control surfaces when the aircraft becomes inverted.

A fourth of the aircraft system operational changes in response toinverted flight pertains to the ailerons. During upright flight, inresponse to roll inputs from the manual controller 205, the stationcontrol system 305 generates communication signals 209 to the aircraftcontrol system 303, which in turn controls the one or more ailerons 127under typical and known flight protocols for aircraft ailerons. When theaircraft transitions to inverted flight, the system control system 301(either in the aircraft control system 303 or the station control system305) alters the control of the ailerons to automatically deflect thetrailing edge of both of the ailerons toward the upper surface of thewing (i.e., gravitationally downward in the inverted orientation) toeffectively operate as flaps 439, i.e., they operate as flaperons thatare extended as an inverted flight flap. It should be recognized thatwhile flaperons are known, it is not known for a control surface tooperate a flaperon as an inverted flap when an aircraft becomesinverted.

This change in aileron operation may be accomplished based upon thegeneration or receipt of a communication signal 209 indicating theauto-land button 211 has been activated (and/or the auto-land functionhas been activated), or in response to a direct sensing that theaircraft is in the inverted orientation. As should be apparent, thischange provides for the aircraft to better prepare for a controlledlanding without further input by the user.

A fifth of the aircraft system operational changes in response toinverted flight pertains to propeller operation. During upright flightthe aircraft control system 303 operates the propeller 135 to providethrust that propels the aircraft. When the auto-land function isactivated (and the aircraft transitions to inverted flight), the systemcontrol system 301 is configured to stop the rotation of the propeller441 in preparation for landing. Moreover, the system control system isconfigured to establish and maintain the propeller in a safe mode, i.e.,a substantially horizontal orientation (i.e., normal to a verticalgravitational direction when the aircraft is in the invertedorientation).

This change in operation of the propeller may be accomplished based uponthe generation or receipt of a communication signal indicating theauto-land button has been activated (and/or the auto-land function hasbeen activated), or in response to a direct sensing that the aircraft isin the inverted orientation. Moreover, it may be done instantaneously,or it may be delayed. The delay may be based upon the aircraft inversionmaneuver being completed, upon the passage of a limited period oftransition time, and/or on the elevation of the aircraft above theground. As should be apparent, this change provides for the propeller tobe safely oriented with respect to the ground prior to landing, therebylimiting the risk of propeller damage during landing, without requiringany further user input.

In a sixth of the aircraft system operational changes in response toinverted flight, when the auto-land button 211 is activated (i.e.,selected, either manually or electronically) (and/or the auto-landfunction is activated) and the aircraft transitions to inverted flight,a stall initiation system is activated. The system control system 301includes the stall initiation system, which is configured to adjust theelevator such that the inverted aircraft pitches its nose upward (withrespect to gravity) to an such extent that the wing is at leastpartially stalled, and perhaps be in deep stall, while flying in theinverted orientation.

This change in operation of the propeller may be accomplished based uponthe generation or receipt of a communication signal indicating theauto-land button has been activated (and/or the auto-land function hasbeen activated) and that the aircraft has completed its control surfacesequence to invert the aircraft, or in response to a direct sensing thatthe aircraft is in the inverted orientation. Moreover, it may be doneinstantaneously, or it may be delayed. The delay may be based upon theaircraft inversion maneuver being completed, upon the passage of alimited period of transition time, on the identification of a landingtarget that is properly positioned for a steep landing approach. Thischange provides for the stalled aircraft 417 to steeply descend 419(see, FIGS. 8 & 9) to the ground while still having some lift to limitand control the descent using the elevator 115 and rudder 117.

In a seventh of the aircraft system operational changes in response toinverted flight, when the auto-land button is activated 445 (and/or theauto land function was activated) and the aircraft transitions toinverted and stalled flight, the system control system operates anactive targeting system that adjusts the elevator and rudder such thatthe inverted and stalled aircraft descends to a target landing location.More particularly, the elevator is controlled to control the depth(i.e., extent) of the wing stall, and thus the angle of descent.Additionally, the rudder is controlled to control the direction of thedescent. It should be noted that the identification of a target landinglocation can be based on a variety of cues, such as GPS coordinates,visual references and/or the identification of a target landing locationby a user using one or more of the various cameras of the aircraft.

The system control system may be further configured for the user tomanually override the control of the control surfaces using thecontroller. Alternatively, the system control system could lack anactive targeting system, and the user could be responsible for manuallyguiding the aircraft to the target landing location.

In an eighth of the aircraft system operational changes, an absolutealtitude determination system within the system control system isactivated 447 for use in the inverted and stalled flight. Themeasurement of true altitude (i.e., above mean sea level) is well knownfor aircraft. During flight over terrain that is not well known, theabsolute altitude (i.e., the altitude above ground level, a.k.a.

the height) might not be known even though the true altitude is known.The system is configured to calculate absolute altitude for an aircraftthat is changing altitudes.

The absolute altitude determination system will include a rate of truealtitude change system (e.g., a rate of descent system) thatcalculates/estimates the rate of true altitude change using air pressureor other known methods of altitude change measurement. The absolutealtitude determination system is further configured to monitor areal-time image of a fixed-size object on the ground, and measure itsrate of change (i.e., using a camera to repeatedly image the fixed-sizefeature, and calculating an imaged size of the feature, such as bymeasuring the proportion of the image filled by the feature). The closerthe aircraft is to the ground, the faster the image will change for agiven rate of descent (or ascent), so the system calculates a rate ofchange in the imaged size (over time). The absolute altitudedetermination system calculates/estimates the (absolute) altitude abovethe ground using a rate of change of the monitored ground image and theestimated rate of change in the true altitude, such as by geometricalcalculations that are within the skill in the art. Advantageously, thismay provide for better control over the landing site of the aircraft,regardless of whether the aircraft is being controlled by an activetargeting system or the user.

It should be noted that the timing of any of these operational changes,individually or combination, may be based upon or altered by additionaluser signals. For example, prior to activating the auto-land button, theuser could be allowed to adjust a delay time for the stall untilreaching a certain altitude, or until the user activates the auto-landbutton a second time.

Methods of Operating the Aircraft

While the aircraft system preferably includes some or all of theabove-identified features, it should be noted that a skilled user canconduct methods of the invention without the use of a control systemthat extensively simplifies the landing process. Moreover, if theaircraft system does include some or all of the control system features,the user conducts the various methods of the invention by initiating theactions taken by the control system (e.g., by activating the auto-landbutton or otherwise causing the auto-land function to be activated).

With reference to FIG. 12, a user may conduct a method of landing anaircraft at a location for landing. As previously described, theaircraft has a wing including an upper surface and a lower surfacedefining an upright orientation for normal aircraft flight, and aninverted orientation for inverted flight. The upper surface isgravitationally above the lower surface while in the uprightorientation, and the lower surface is gravitationally above the uppersurface while in the inverted orientation.

The method includes the steps of: (a) controlling the operation of oneor more control surfaces to approach the landing location while theaircraft is flying in the upright orientation 501; (b) controlling theoperation of the one or more control surfaces to invert the aircraftsuch that it is controllably moving in an inverted orientation 503; and(c) controlling the operation of the one or more control surfaces todescend the aircraft to the landing location in the inverted orientation505.

Under this method, a downward facing payload can be protected from thehigh impact loads that are possible from a direct impact with theground. Nevertheless, some flight control is maintained such that thelanding location can be controlled in flight conditions characterized byunknown or changing wind speeds and/or directions. Moreover, this allowsa user of relatively limited skill or experience from having to committo a landing attempt at a high altitude without any ability to adjustfor mistakes.

Generally, the aircraft will be an unmanned aircraft, and the steps areconducted by a user operating a remote-control station configured forremotely controlling the operation of the one or more control surfaces.Typically, as was described above, the aircraft will include a first,upright-orientation camera oriented to view downward and forward whilethe aircraft is in the upright orientation, and a second,inverted-orientation camera oriented to view downward and forward whilethe aircraft is in the inverted orientation. On the remote-controlstation, the user observes images from the first camera while flying inthe upright orientation, and from the second camera while flying in theinverted orientation.

While any of a variety of maneuvers may be used to invert the aircraftin step (b), it is anticipated that two advantageous maneuvers are tooperate the one or more control surfaces (e.g., the ailerons) to rollthe aircraft into the inverted orientation, and to operate the one ormore control surfaces (e.g., the elevators) to pitch the aircraft intothe inverted orientation. The roll maneuver provides for the aircraft tobe in substantially the same location, and traveling in substantiallythe same direction after the maneuver is completed. This simplifies theuser experience, as the ground image remains unchanged when the aircraftswitches from the upright-orientation camera to the inverted-orientationcamera (assuming the aircraft is using such cameras).

The pitch maneuver provides for the aircraft to be traveling in theopposite direction, and might be accompanied by a significant change intrue altitude. Moreover, the change in direction of travel will cause aninversion of the ground view from the aircraft (and on theremote-control station display). Nevertheless, this maneuver might bepreferable in situations where the aircraft is traveling back from andlanding close to dangerous airspace, such as to a user on a battlefieldor close to a burning building.

The aircraft may include a starboard light emitting a first color (e.g.,green) on a starboard side of the wing and a port light emitting asecond color (e.g., red) on a port side of the wing. The method of thisembodiment may also include the switching of the colors such that thestarboard light emits the second color (e.g., red) and the port lightemits the first color (e.g., green). This switching may be manually andindividually initiated by a user, or may be an automated process inresponse to some other condition controlled by the user.

Optionally, the user may manually and individually initiate a change inthe operation of ailerons such that they become flaperons in theinverted orientation, i.e., the ailerons deflect to operate as flaps509. This switching may be manually and individually initiated by auser, or may be an automated process in response to some other conditioncontrolled by the user.

Additionally, the user may stow the propeller, i.e., stop the rotationof the propeller in preparation for landing, and have it positioned andmaintained in a substantially horizontal, safe mode orientation 511(i.e., normal to a vertical gravitational direction when the aircraft isin the inverted orientation). This propeller control may be manually andindividually initiated by a user, or may be an automated process inresponse to some other condition controlled by the user.

Furthermore, the user may initiate an absolute altitude determinationsystem that determines the absolute altitude of the aircraft as itdescends, and optionally displays the altitude on the remote-controlstation for use by the user. The absolute altitude determination systemcalculates an estimated altitude above the ground using a rate of changeof a monitored ground image and an estimated rate of descent 513. Thisaltitude determination system control may be manually and individuallyinitiated by a user, or may be an automated process in response to someother condition controlled by the user.

In landing the aircraft at the landing location, the user may controlthe operation of one or more control surfaces to at least partiallystall the wing 515 while the aircraft is in the inverted orientation toprovide for the aircraft to rapidly descend. The user may furthercontrol the rate of the descent of the aircraft by controlling depth ofthe wing stall. In at least some cases, a deep stall will be desirable.During descent, the direction of the decent may be controlled bycontrolling the rudder.

Optionally, some or all of these functions that may be initiated by theuser by activating one or more buttons (on the remote-control station)that initiate the system control system to activate/conduct thesefeatures and functions, including the operation of the control surfacesto invert the aircraft, the changing of the light colors, the use ofinverted flaperons, the stowing of the propeller, the activation of thealtitude determination system, the stalling of the wing, and thecontrolling of the rate of descent and direction of descent. Thebutton(s) may instruct the aircraft control system to automaticallyconduct an inverting maneuver in which the aircraft rotates from theupright orientation to the inverted orientation, change the colors ofthe landing lights, extend the elevators as flaperons, stow thepropeller, activate of the altitude determination system, stall thewing, and/or control of the rate of descent and/or direction of descentin any variation of combinations.

It is to be understood that the invention comprises apparatus andmethods for landing an aircraft, and for producing and selling aircraft,as well as the apparatus and methods of the aircraft itself. Alternatevariations of these embodiments could comprise other types of aerialvehicles. In short, the above disclosed features can be combined in awide variety of configurations within the anticipated scope of theinvention.

While particular forms of the invention have been illustrated anddescribed, it will be apparent that various modifications can be madewithout departing from the spirit and scope of the invention. Thus,although the invention has been described in detail with reference onlyto the preferred embodiments, those having ordinary skill in the artwill appreciate that various modifications can be made without departingfrom the scope of the invention. Accordingly, the invention is notintended to be limited by the above discussion, and is defined withreference to the following claims.

1. A method of rapidly descending an aircraft to land at a landinglocation, the aircraft having a wing including an upper surface and alower surface defining an upright orientation for normal aircraftflight, and an inverted orientation for inverted flight, the uppersurface being gravitationally above the lower surface while in theupright orientation, and the lower surface being gravitationally abovethe upper surface while in the inverted orientation, comprising: (a)controlling the operation of one or more repeatedly controllable controlsurfaces to approach the landing location while the aircraft is flyingin the upright orientation; (b) controlling the operation of the one ormore repeatedly controllable control surfaces to invert the aircraftsuch that it is controllably moving in an inverted orientation; (c)controlling the operation of the one or more repeatedly controllablecontrol surfaces to at least partially stall the wing while in theinverted orientation to provide for the aircraft to descend in a rapiddescent; and (d) after step (c), further controlling the operation ofthe same repeatedly controllable control surfaces that inverted theaircraft, to control the rapid descent of the aircraft.
 2. The method ofclaim 1, wherein step (b) includes controlling the operation of the oneor more repeatedly controllable control surfaces to roll into theinverted orientation, and wherein in step (d), the operation of the samerepeatedly controllable control surfaces controls the roll of theaircraft during the rapid descent of the aircraft.
 3. The method ofclaim 1, wherein step (b) includes controlling the operation of the oneor more repeatedly controllable control surfaces to pitch into theinverted orientation, and wherein in step (d), the operation of the samerepeatedly controllable control surfaces controls the pitch of theaircraft during the rapid descent of the aircraft.
 4. The method ofclaim 1, wherein the one or more repeatedly controllable controlsurfaces include one or more repeatedly controllable elevators on anempennage, wherein step (c) includes controlling the operation of theone or more repeatedly controllable elevators to at least partiallystall the wing while in the inverted orientation, and wherein in step(d), the operation of the same repeatedly controllable elevatorscontrols the pitch of the aircraft during the rapid descent of theaircraft.
 5. The method of claim 1, wherein step (c) includescontrolling a rate of the rapid descent by controlling depth of the wingstall.
 6. (canceled)
 7. The method of claim 1, wherein the one or morecontrol surfaces include a repeatedly controllable rudder on anempennage, and wherein step (d) includes controlling a direction of therapid decent by controlling the repeatedly controllable rudder.
 8. Themethod of claim 1, wherein the aircraft uses a propeller for propulsion,and further comprising the step of (d) stopping and maintaining thepropeller in a substantially horizontal orientation prior to theaircraft reaching the landing location.
 9. The method of claim 1, andfurther comprising a starboard light on a starboard side of the wing anda port light on a port side of the wing, and further comprisingcontrolling the color of the starboard and port lights such that thestarboard light emits a first color and the port light emits a secondcolor while the aircraft is in the upright orientation, and such thatthe starboard light emits the second color and the port light emits thefirst color while the aircraft is in the inverted orientation.
 10. Themethod of claim 1, wherein the aircraft is configured with repeatedlycontrollable ailerons, and further comprising deflecting the repeatedlycontrollable ailerons to operate as repeatedly controllable flaps whenthe aircraft is in the inverted orientation.
 11. An unmanned aircraftsystem, comprising: an aircraft including a wing having an upper surfaceand a lower surface defining an upright orientation for normal aircraftflight and an inverted orientation for inverted flight, the uppersurface being gravitationally above the lower surface while in theupright orientation, and the lower surface being gravitationally abovethe upper surface while in the inverted orientation, and furtherincluding one or more control surfaces; a remote-control station; and aremote-control control system configured for a user to remotely controlthe flight of the aircraft using the remote-control station; wherein theremote-control station is provided with an auto-land function thatinstructs the control system to automatically control the one or morecontrol surfaces such that the aircraft conducts an inverting maneuverin which the aircraft rotates from the upright orientation to theinverted orientation, and such that the wing is at least partiallystalled while the aircraft is in the inverted orientation.
 12. Theunmanned aircraft system of claim 11, wherein the control system isconfigured to control the one or more control surfaces such that theaircraft conducts an inverting maneuver that rolls the aircraft into theinverted orientation.
 13. The unmanned aircraft system of claim 11,wherein the control system is configured to control the one or morecontrol surfaces such that the aircraft conducts an inverting maneuverthat pitches the aircraft into the inverted orientation.
 14. Theunmanned aircraft system of claim 11, wherein the one or more controlsurfaces include one or more elevators on an empennage, and wherein thecontrol system is configured to control the one or more elevators tocause the wing to be at least partially stalled while the aircraft is inthe inverted orientation.
 15. The unmanned aircraft system of claim 11,wherein the control system is configured to control an aircraft rate ofdescent by controlling depth of the wing stall.
 16. The unmannedaircraft system of claim 11, wherein the control system is configured toestimate the rate of descent, monitor a real-time image of the ground,and calculate an estimated altitude using a rate of change of themonitored ground image and the estimated rate of descent.
 17. Theunmanned aircraft system of claim 11, wherein the one or more controlsurfaces include a rudder on an empennage, and wherein the controlsystem is configured to control a direction of the decent by controllingthe rudder while the aircraft is inverted.
 18. The unmanned aircraftsystem of claim 11, and further comprising a propeller configured forpropulsion of the aircraft, wherein the control system is configured tostop the propeller and maintain it in a substantially horizontalorientation as a result of the auto-land function being activated.